sql server 2005 error

Question

I am new to t-sql in the last few months. I am getting the following error in sql server 2005 and would like to know how to get around the problem:
 Msg 4104, Level 16, State 1, Line 1
The multi-part identifier "Z.MaxReceiveDate" could not be bound.
The sql that I am running is the following:
select distinct  Z.gnumber, R.Requests, Z.MaxReceiveDate
     
   from
  
 (select distinct gnumber,              
            count(*) as Requests
    from dbo.table1
            where receive_date > Z.MaxReceiveDate
   group by  gnumber
        ) R
 
left join
(select distinct  P.gnumber,
             MaxReceiveDate = Max(Received_Date),
             from dbo.table2
    group by  P.gnumber
 ) Z
On Z.HNumber = R.Hnumber
I am bascially trying to use the maxreceivedate value from a subquery.
Can you suggest ways to solve this problem?
Thanks!